Aircraft landing gear construction



MarchZZ, 1949. A. M FRANcl-u AIRCRAFT LANDING GEAR CONSTRUCTION 5Sheets-Sheet 1 Filed. Feb. 14, 1942 :Nv NToR /44-00 /PA/vcf/A BW arch22, 1949. A, M FRANCHl AIRCRAFT LANDING GEAR CONSTRUCTION I 3Sheets-Sheet 3 Filed Feb. 14, 1942 Patented Mai". 22, 1949 AIRCRAFTLANDING GEAR CONSTRUCTION Aldo M. Franchi, New York, N. Y., assignor ofone-half to James T. Murphy, New York, N. Y.

Application February 14, 1942, Serial No. 430,954

Claims. l

This invention relates to aircraft landing gear construction.

One of the objects of this invention is to provide a simple, practicaland eicient wheel construction and mounting for aircraft, moreparticularly for the tail end of airplanes, that will be of dependableaction under the varying conditions of practical use. Another object isto provide a construction of the above-mentioned character that will besimple to manufacture, capable of embodiment in light-weight yet strongform, capable of ready incorporation into aircraft construction, andcapable of ea-se of assembly and disassembly. Another object is toprovide a construction of the above-mentioned character in which thepeculiar and sometimes sudden and severe strains and stresses that occurupon making a landing can be safely and reliably transmitted andabsorbed or dependably counteracted by both wheel and its mounting andcertain reliable coactions therebetween.

Another object is to provide a construction of the above-mentionedcharacter arranged and constructed as a unit for ease and speed ofassembly or disassembly relative to the aircraft itself and embodying,according to desire or circumstances, dirigibility or retractability orfree caster-wheel action. Another object is to provide -a constructionof the above-mentioned character in which retractability or extension ofthe mounting for the landing element may be dependably -and reliablyachieved and controlled, and by mechanism that will be simple, strong,inexpensive and foolproof and positive in action. Another object is toprovide for the dependable and simple locking or unlocking of themounting in retracted or extended position and for the dependable andpositive control thereof.

Another object is to provide a construction of the above-mentionedcharacter in sub-unit or sub-assembly form or forms to facilitateassembly, repair, replacement or disassembly, or to achieve widerexibility or adaptability of incorporation into an aircraft according,for example, to such factors as whether or not dirigibility crretraction or free caster-wheel vaction or any thereof is desired.Another object is to make possible structural standardization of certain-.subunits or sub-assemblies to facilitate ready interchangeability,including interchangeability as between aircraft structures with orwithout .dirigibilityg with or without retraction, or with or withoutyfree caster-Wheel action. Another Objectis to provide a construction ofthe above-mentioned character in which dependable control of forces suchas occur in making a landing can be achieved in a simple and foolproofmanner. Another object is to provide a construction of the just-statedcharacter which will have wide range of suitability to diierentconditions in practice, such as load, impact, landing speeds, and thelike, and in which compensation or setting for su-ch diierent conditionscan be quickly and simply eiected.

Another object is to provide a construction of the above-mentionedcharacter that will have good durability throughout the hard and varyingconditions of practical use and which will lessen the maintenance workand maintenance costs. Another object is, in general, to provide aniinproved con-struction and mounting for landing devices such as wheelsused by aircraft. Other objects will be in part obvious or in partpointed out hereinafter.

The invention accordingly consists in the features of construction,combinations of elements, and arrangements of parts as will beexemplified in the structure to be hereinafter described, and the scopeof the application of which will be indicated in the following claims.

In the accompanying drawings in which are shown several of the variouspossible embodiments of my invention,

Figure 1 is a side elevation of a landing device in the form of a wheelwith its mounting'to the aircraft frame, only portions of which areshown, certain parts being broken away to better show certain otherparts;

Figure 2 is an end elevation as seen from the left in Figure 1, certainof the parts being shown in central vertical cross-section, and othersbeing broken away or omitted;

Fig. 3 is a View as seen along the line 3 3 of Figure 2, certain partsbeing shown in section and others in elevation, and certain other partsbeing omitted or broken away, showing one form of sub-unit construction;

Figure 4 is a View like that of Figure 3 but showing another form ofsub-unit construction;

Figure 5 is a transverse sectional view as seen along the line 5 5 ofFigure 1;

Figure 6 is a side elevation showing another mounting arrangement forthe landingdevice and its main support; and

Figure 7 is a plan view thereof as seenfrom above in Figure 6. f

Similar reference characters refer to similar parts throughout theseveral views of the drawings:

Referring first to Figures 1 and 2 of the drawings, I have generallyindicated by the reference character I part of the frame of an aircraftwhich may take any suitable form, but for purposes of illustration, letit be assumed that the frame I0 is part of the rear or tail frame of anairplane and that the landing devices are in the form of wheels of whichat least one is to be at the tail end of the craft, illustratively theWheel generally indicated by the reference character I I, though it willbe understood that certain features of my invention are not limited tothe tail wheel or wheels and are applicable at points other than thestern or tail of the craft and useable with devices other than wheels,such as skids, pontoons or the like. Where the landing device is to beretracted, as during iiight, I preferably provide a sub-assembly orauxiliary frame generally indicated by the reference character i2 andconstructed for ready incorporation into or with the frame I0 of thecraft.

Thus the auxiliary frame I2 may comprise preferably two spaced arcuateelements I`3 and I4 held in spaced and parallel relation in any suitablemanner illustratively and preferably by mountings upon or attachment toelements of the main frame I0.

For example, where the main frame I0 may have two upper spaced andusually parallel elements I5 and I6 and two lower spaced and parallelelements l'I and I8, usually and illustratively tubular, the forward orright-hand ends I3a and I'41 of the auxiliary frame elements I3 and I4respectively may be extended into respective parallelism to the frameelements I5 and I6 to which they may be respectively secured in anysuitable manner, illustratively as by brackets 2-I and 22 of suitableconformation and construction, illustratively like that shown in thedrawings.

Thus, for example, each bracket may have a base portion 23 to restatwise against the auxiliary frame element to which it may be secured asby rivets 24 and may have a split and hence separable sleeve 25dimensioned to encompass the main frame element such as the element l5,the two halves of the sleeve being then drawn and held together as bybolts 26, thereby to clamp securely therein the element of the craftframe. By such a construction, the forward or righthand ends of theauxiliary frame elements I3 and I4, as viewed in Figure 1, may bequickly and dependably attached to the main frame, the split clampingsleeve construction permitting also ready setting of the auxiliary frameat the desired point lengthwise of the parallel frame elements I5-I'6.

The rear or left-hand ends of frame elements I3 and I4, as viewed inFigure l, are secured respectively to the lower parallel frame elementsI'I and I8, preferably by generally similar brackets as just describedabove and respectively indicated by the reference characters 21 and 28.The latter also have at or base elements 23 secured to the auxiliaryframe element in any suitable way as by rivets 24 and are provided withseparable split sleeves 25 to encompass the frame elements II and I8respectively, whence bolts 26 securely clamp the craft frame elementsbetween the parts of the sleeves.y y

A suitable extent of each of the frame elements I'3 4and I4,is curvedalong the arc of a circle, illustratively as indicated in Figure 1, toan extent of about 90, and in at least one of them, illustrativelyelement I3, and preferably along the under edge thereof as seen inFigure 1 I provide notches or cut-outs, preferably of substantialproportions, as indicated at 3I and 32, positioning them atsubstantially the extremes of the arcuate extent. Hence the cut-outs3I-32 are about 90 apart, where a 90 swing of the landing devicesuiiices for retraction or extension.

At the axis of curvature of the frame elements I3-I4, I provide twospaced bearings 33 and 34 for the pivotal support of a sub-unitpreferably in the form of a housing generally indicated at 35, and thispivotal support preferably comprises two trunnion or shaft elements 31and 38 supported at their outer ends in the bearings 33 and 34respectively andA secured at their inner ends to the housing 35preferably in a manner later described. Housing 35 has suitable means,such as an arm 40, extending therefrom and supporting at its outer endthe landing device such as the wheel II, all preferably, in the mannerlater set forth.

The bearing members 33,--34 are suitably' mounted or secured at theaxisof the parallel and aligned auxiliary frame elements I3 and I4 and,as better appears from Figures 1 and 2, I1 may utilize, for thispurpose, the lower frame. elements I'I and I8 of the craft frame IIJ;

Thus, for example, each bearing member 33-34 terminates at its outer endin a split or clamping sleeve 4I- withr which to encompass-respectivelythe craft frame elements I'1 and4 I8 which are securely clamped withinthe sleeves by the bolts 42 which draw the sleeve parts together andthus dependably grip the frame elements.

At the upper end of the housing structure 35, I provide bracket-likearms 43 and 4'4 (Figure 2') mounted and secured as is later describedand terminating in sleeve-like or box-like housings 45 whichrespectively embrace the frame elements -l3 and I4, having an internalcross-section substantially similar to the cross-section of the frameelements which they embrace, illustratively rectangular and preferablyof the same curvature, and preferably proportioned so as to formtherewith a sliding t.

For convenience of assembly and disassembly, the box-like guide elements45-45 are made in separable parts, preferably two in number, the outerpart 45a being'preferably in the form of a plate detachably secured inposition as by the screws 46, the plate part 45a overlying the outerface of the auxiliary frame element to which its companion box-like partis slideably related.

Accordingly, the housing structure 35, with its arm 40 and wheel II mayfreely pivot about the axis of the spaced bearings 33--34 and throughoutan angle according to the arcuate extent of the curved portions of theauxiliary frame elements I3^Ifs and I preferably limit the extent ofthis pivoting movement byl the coaction with the cut-outs 3Iand 32 loffastop element/i1, shown in Figure 1 as bottoming in the cut-out 3f, andcarried and controlled in av manner later described.

In making a landing, the landing device such as the wheel I I is inextended position and vihence in the positionshownv in Figure 1', thedirection of travel of the craft being from the-rightto the left and theabove-described assembly of -the'various parts to the craft frameelements achieves a desirable distribution throughout thelatter, il'-lustratively four o fthem (illustratively elements I5-I5-I'I-I8; ofIFigurevZ), the illustrative assembly above described providingat-"leastsixrdia tributed points at or through which landing impact,preferably cushioned and controlled in the manner later described, istaken up by the craft frame or by or through which the normal load to becarried by the wheel or like structure is ltransmitted to the latterfrom the craft itself, thus avoiding undue concentration of such forcesor reactions or strains and stresses resulting therefrom. Moreover,these numerous and relatively widely distributed points, because of therelationship of the yparts -thereat secured to the frame elements, willbe seen also to greatly reinforce and strengthen the craft framestructure `and -thus better condition it to stand up under the strainsand stresses like those above mentioned.

Thus, for example, and as is later more clearly brought out, the.transverse elements 31-38 and 43-44 of Figure 2 are rigidly securedtogether and to the frame structure 35 so that each takes part intransmitting or receiving strains or stresses relative to the craftframe and relative to the auxiliary frame elements 53-13, and togetherwith the latter, which are -anchored to both the upper and lower pairs l5-l 6 and i 'l-l8 of the craft frame l0, aid and c-oact in distributingstrains and stresses from or to the craft frame at the severaldistributed 'points of attachment earlier above described.

The housing structure 35 is preferably constructed, for facility ofassembly and facility or flexibility of adaptation, in several,preferably two, sections and in Figure 2 the two sections are indicatedat 5I and 52, being preferably symmetrical or identical and at theirmating or contacting edges they have suitable extensions such :i

as lugs or ears 53 (see also Figures 3 and 4) suitably apertured toreceive bolts or screws 54 whereby the two casing yparts 5|-52 may berigidly secured together.

The side walls of the ycasing parts {il-52 are suitably thickenedadjacent their lower central portions to receive therethrough a bol't 55having :a head 56 shaped to provide an eye 5l and receiving on itsthreaded end a nut 58 shaped to provide an eye 59; the bolt may assistin holding the two casing Iparts together and, bridging across thehollow interior of the casing 35, it forms a pivotal support for the armlil! which is provided at its inner and upper end, in -any suitable way,as by forming integrally therewith, with two spaced abutments 6l and 62,each to one side of the axis of the pivot stud or bolt 55 and presentingfaces t l a and E522l of suitable configuration and area, substantiallyas shown in Figure 3, to form seats for the lower ends of helicalsprings 65 and 65 respectively. These springs .are housed and guided incylindrical chambers or cylinders 'Bl and 68 respectively, the walls ofwhich are integral with the casing vstructure 35, and where the latteris in two parts such as parts 5| and 52, each part has integrally formedwith it half or a 180 extent of each of the two cylinders so :that whenthe two halves yare assembled, with Ethe springs laid into theirrespective cylinders, the springs become housed in their respectivecylindrical chambers and each is by its cylinder, which is open-ended atthe lower end as viewed in Figure 3, thus also assembled to .therespective abutments {il-52 of the arm; the arm 50, as is better shownin Figure 3, -is bored out or drilled las at a, intermediate of theabut-ments iii-62 and is `offs-uitable length in the direction of theaxis of the pivot pin 55 to provide a long and good bearing surface,preferably extending between the opposed lateral walls of the housing 35as viewed in Figure 2 so as to be free from end play.

The two housing yparts 5I-52 are open or cut away, ypreferably on bothsides of the vertical axis as seen in Figures 3 and 4 and as indicatedat 'l0 and 'H so as to 'provide suitable openings in the lower end ofthe casing 35 through either of which .the arm 4i! may extendwithadequate clearance according to the range of pivoting of the arm aboutthe pivot -pin 55. Assembly of the arm to the casing is preferablyachieved by laying the upper part of the arm in one casing section, thenlaying the springs in place as above described, and then laying theother casing section thereover and securing the two casing sectionstogether as by the bolts 54 and the pivot bolt 55 which is threadedthrough the openings in the casing side walls and also through the bore40 of the arm.

As will be seen from Figures 2, 3 and 4, the :casing structure 35 hasextending from it, at its upper and lower ends and along its centralvertical axis, cylindrical studs 'l2 and 'I3 preferably integrallyformed therewith, and where the casing structure is in, for example, twoparts like the parts Fil-52, one-half or a extent lof each of the studs'l2 and I3 is integrally formedl with each casing section, the halvesbecoming properly -aligned and assembled when the two casing sectionsare fastened together as above described. Where lightness of weight isdesired, these studs are preferably hollow and hence annular incrosssection, having in effect a tubular conformation. Each casingsection may conveniently be in the form of a casting of suitable metal,and its conformation and machining where necessary will be seen to lendthemselves readily Ato manufacture in that manner.

Preferably, by means of the studs 'l2-13, the assembled sub-unit ismounted in position and as will be more clearly brought out hereinafterit will be seen that a variety of different practical requirements orconditions may be thereby easily met. For example, let it be assumedthat the landing device is to be both retractible and dirigible; in suchcase I prefer to utilize the studs 'l2- '83 to mount this sub-unit inthe cross arms 3!-38 and 43-44 above described in connection with Figure2, and an illustrative and preferred manner of achieving such a mountingis better shown in Figures 2 and 1.

Thus, referring to Figure 2, the studs or arms 31-38 have rigidlysecured to them at their inner ends a cup-like bearing housing l5 withinthe cylindrical wall 'I5a of which is fitted the outer race 16 of asuitable anti-friction bearing whose inner race 'll has an insidediameter to be received over the casing stud 13, the bottom wall 15b ofthe housing l5 having a hole to take over or about the stud 13 with asuitable amount of clearance. The lower end of the stud 13 is threadedto receive a nut I3 for holding the bearing assembly clamped in placebetween itself and the shoulder 'i3a (Figures 3 and 4) The bearingstructure 'l5-'l1 is of any suitable form or construction, preferably ofthe combined radial and thrust type and hence the companion faces of theraces may be frusto-conical as indicated in Figure 2, with suitablyshaped rollers 19 therebetween.

In a generally similar manner arms 43 and 44 have secured to their innerends a bearing hous'- ing 8| whose outer cylindrical wall 8|a has fittedinto it the outer race 82 of an anti-friction bearing preferablyidentical to the one above described andhence having also an inner race83, being of the combined radial and thrust type and hence' preferablyhaving contiguous frusto-conical faces between which are the rollers 84.

Race 83 is bored out to be litted snugly onto the upper stud 12, takingagainst the shoulder 12.a (Figures 3 and 4) of the stud, while thecompanion wall SIb of the bearing housing 8| has a hole to take over thestud 13 but with a suitable amount of clearance therebetween.

The outer end of the stud 12 is threaded to receive a nut 85 by whichthe bearing assembly may be clamped against the shoulder 72a.

With such a mounting, the above-mentioned sub-assembly of housing 35 andarm all with wheel Il is dependably mounted for rotation about thecoincident axes of the studs I2- 13, whence also the wheel Il, havingits horizontal axis of rotation substantially displaced (see Figure l)from the vertical axis of the casing studs 'l2- 13 and about which axisthe structure may pivot, is permitted freely to caster or follow wheresuch a castering action is desired.

Where dirigibility is, however, desired, suitable means may be employedto control the swing of this sub-assembly about the above-mentionedvertical axis and, for example, suitable rods or wires (not shown) maybe attached to the eyes 51 and 59 (Figure 2) and led oil? to a suitablemanual or other control. may provide two sheaves 83 and 3Q, mountedpreferably co-axially with the vertical axis of the casing structure 35,as, for example, by fitting them onto the stud 'l2 and interposing thembetween the bearing assembly and the nut 65, the latter with theshoulder 12a thus holding the sheave structure assembled to the casing.If desired, suitable means such as a key 9G (Figure 2) may be employedto insure against relative rotation between the stud 'l2 and the sheavesi3- 89.

To the grooves of the sheaves Se 35i are related flexible elements 5land 92, such as cable, the one, as indicated in Figure l, extendingclockwise about part of the sheave 88 and the other extendingcounter-clockwise about part of the sheave B9, their respective endsbeing anchored to the sheaves at suitably displaced points, the cables9l-92 being led ofi to any suitable operating or control mechanism, notshown, and suitably arranged to haul in on one cable while paying outthe other at the same rate, and, of course; reversibly.

In any such case of dirigibility, there is achieved nicety of ease ofvertical pivoting, the substantial vertical spacing between the' upperand lower bearing structures (see Figure 1) coupled with the preferredform and arrangement of the bearings themselves coacting for thesepurposes.

The vertical spacing between these bearings, however, and theirinterrelationship to the other parts insures also dependable action intransmitting, in one direction or the other, such strains and stressesor forces as result from the normal load imposed upon the wheel or asresult from impact when the wheel or other landing device carried by thearm di) contacts the ground. Particularly in making a landing, theforces or stressesset up can greatly vary in direction, magnitude andcharacter. For example, though the horizontal axis of the device such asthe wheel l I carried by the arm Ml may be neatly lined up 'transverselyof the longitudinal axis of the craft,

the latter in approaching the land or the like mayhave its longitudinal'axis at an angle to the Or, as is preferred, I

actual direction of craft night or movement, andy in such case thereresult also substantial lateral or side thrusts both on the device Il(Figure 1) andl through the arm il they are transmitted to the casingstructure and to related parts. Here, however, the substantial verticalspacing of the bearing structures (Figure 2) makes it possible better toresist such side thrusts, and' thus the tension, compression or bendingstresses on such elements as the parts 31-38 and i3-44 are greatlylessened and such parts may be made of lighter construction ormaterials, while the auxiliary frame members l-Ill materially strengthenthe craft frame l0 and its elements and by the aboveementionedmultiplicity of points of attachment of the casing structure 35, suchstresses are precluded from being concentrated detrimentally and becomein eiect widely distributed and thus more easily absorbed or resisted.

The construction and mounting of the device Il, illustratively in theform of a wheel is preferably made to take part in these coactions,particularly in itself resisting such out of line or torsional or sidethrusts or impacts and in transmitting them, without damage to itself,to the arm di) and to the housing structure 35 and related parts asabove described. Thus, turning to Figure 5, arm @it terminatespreferably in a fork having two arms and (idc preferably providing asubstantial spacing therebetween and suitably apertured to receive theends of a shaft 55 threaded at both ends to receive lock nuts S, thus toprovide for ready assembly or disassembly.

I provide a hub means of substantial axial length to be received betweenthe arms lieb and 43, and to provide for ready assembly anddetachability of the contacting device itself, such as the wheel iiwhich can be in the form of any suitable tire of a ma al like rubber,either solid or inflated, I prefere] maire the hub means in two partseierably ci identical construction. Thus each is recessed at its outerend as at Q9 to receive and have fitted therein the outer race lili ofan anti-:friction bearing preferably of the combined radial and thrusttype and hence illustratively having frusta-conical faces on the outerrace i621 and on the inner race |82 with the rollers therebetween.

At the inner ends of these annular end recesses 9d, they are stepped oragain recessed as at l, but to a smaller diameter, and before assemblingthe outer races to their respective recesses 99, a hollow bolt lili isthrust through the recess 99 of one of the members such as the member 98to bring its headed end into the recess E'l and to project its shanlzthrough the hole i3d and into the hole ill of the companion member 9i,the device such as the wheel fi 1g been interposed between the two m 93,which are suitably shaped p erally formed for that purpose somewhat asshown Figiue 5, whence a nut Hi8, accommodated in the recess if'of themember G3, is threaded onto the threaded end of the hollow bolt with theaid, for example, of a Spanner wrench, thus to clamp the members 91 andtogether and also to grip the element such as th wheel l' between themembers Sl and and thus hold it assembled to the hub structure.

Thence the bearing assemblies may be inserted into the recesses oi themembers 92 and 93 and the assembly may now be interposed between thefork arms ib and luc and bolt 95 passed 9 through the holes in the forkarms, through the two inner races |02, and through the hollow boltIIJ'I. The clamping action of the nuts 96 of the bolt 95 may be utilizedto clamp against the arms and to fix the races I'llZ against movementaway from the central plane of the assembly or nuts i526 may be used, inwhich case arms 4th and 46 are each clamped between nuts 96 and IIII).The hole through the hollow bolt Iil'l is preferably larger than thediameter of the shaft 95 so as not to interfere with the bearing actionof the axially spaced anti-friction bearing structures and also So as toaccommodate lubrication, if desired, to be :fed in both directionsaxially to the two bearing structures. Also, if desired, suitable meansgenerally indicated at IIlQ may be used to cover any cushioning actionas may be in the structure i II itself, to the main arm 4E and thus tothe casing structure 35 by which they are distributed and dissipated ortaken up as above described. The substantial radial and axial andpreferably integral extent of the companion members 97 and 98 give themindividually and collectively substantial strength and rigidity and theyand their parts give substantial engagement and support to the wheel ortire II', dependably resisting distortion and dependably transmittingabnormal forces to the axially spa-ced bearing structures and hence tothe arm 4I! and remaining parts. Also, disassembly may be quicklyachieved, for example, for

purposes of replacement or repair of the tire II.r

Moreover, any such side thrusts or impacts are accompanied by or brokendown into components which tend to swing the arm III) incounter-clockwise direction as viewed in Figures 1, 3 and 4, a clean ordirect landing plus the normal load of the craft having a similar butdirect effect. In

any such case, the springs 65 and 66 come into play to absorb andcushion or dissipate materially the energy of such a direct thrust, thuslessening in turn the strains and stresses transmitted by the casingstructure 35 to other parts such as the auxiliary frame and also thecraft frame.

In this connection and referring first to Figure 3, a preferredarrangement and construction of the springs 65 and 66 is such thatnormally, as

for example, without a load being transmitted by the arm 40, the arm 4l!is heldin about the position shown in the drawings, in eifect floatingin normal position under the control of the two springs; in this`relationship spring is preferably a stronger or stiffer spring thanspring 66 and, illustratively where made of the same kind of wire andwound to the same diameter of helix, spring 65 may be in its normalextended or uncompressed condition whilespring 65, preferably made of awire of smaller diameter, is substantially under" Y compression, beingaided in that direction by the tendency of compressed spring 66 toexpand, the

two springs achieving conditions or lengths appropriate to theparticular load and according to the various lever arms that are madeeffective as a result of the proportioning of the various parts of thearm 4I), the lever arms of the abutments ISIa and 62a being in theillustration substantially equal.

Should the landing device at the free end of the lever 4U receive animpact or be subjected to a suddenly applied load, as sometimes occursin making a landing, the substantially uncompressed spring 65 undergoescompression and absorbs or dissipates in the process a substantialportion of the energy of the impact, spring 66 having a tendency to aidin that direction and expanding as the arm il swings incounter-clockwise direction as viewed in, Figures 3 and 4.

As the energy of the impact is thus counteracted or dissipated by thespring 65, which thus has energy stored in it, the tendency of the craftto react and rise somewhat again might receive an 'aiding impulse ofsubstantial character due to the tendency of the spring 65 at the samemoment to expend its stored energy and thus to tend to swing the arm IIJin clockwise direction and thus aid the tendency for upward or reboundmovement of the craft, but such tendency or action on the part of thespring 65 is slowed up or counteracted by the now expanded spring 66,which thus resists tendency of the arm 4I! to be swung in clockwisedirection by the spring 65 and, in absor"ing energy expended by the nowexpanding spring 65. spring 66 insures that the return of the arm 40 toa readjusted position takes place slowly. Thereby tendency quickly tokick the port of the craft supported by the wheel I I, such asA thetail` suddenly or quickly in an upward dir^ctioo, tending to nose thecraft over, is dependably guarded against.

The arrangement abovedescribed and as shown in Figure 3 may servedependably where initially the lever arms and'strengths of the springsand like factors can be initially suited to the load and impact orstrain factors, but according to other features of my invention I makeit possible. with a `given system of leverages and springs to quicklyadapt or suit their actions to any one of a substantial range of load orimpact factors, and an illustrative mode of carrying out these featuresis shown in Figure 4 where again are present the springs 65 and 66capable of functioning and coacting in the manner above described.

In Figure 4, the springs 65 and 66 are preferably housed in orassociated with an expansible and contra'ctible chamber constructed andarranged, under the actionof a controlled fluid. to vary or determinethe actions of the respective springs. Conveniently and preferably, eachof the housing-s is made up of two telescoping elements and eachcontains therein, for comlpactness and also for housing and guidance ofthe spring, one of the springs.

Thus in the cylindrical chamber 61 is slideably mounted and guided oneelement II'I of the telescopic housing and in the upper end of thecasing ystructure 35 is supported the downwardly extending companionelement II8, the latter being received Within the former and suitablepacking, indicated at I I 9, insures tightness against leakage at thejunction between the two housing elements as one moves vaxially relativeto the other. The packing structure IIQ may be of any suitableconstruction, illustratively on the order oi a stuing box or gland.

Spring 65 bottoms against the base of the elescopic housing structure35. each half. section and 52 of which contains, in its upper end wall',half of this round hole, so that the parts ||'|65||8 and other partsthereof. about to be described may, after having been previouslyassembled, be laid into position into one half section of the casing,whence the other half is laid thereover and secured together as aboveearlier described. The upper neck-like portion I8a is externallythreaded to receive a nut which may thereupon be tightened up tosecurely hold the element I-|8 in position co-axially withv thecylindrical chamber 61.

The portion ||8a is, bored out or drilled along its axis and at itsupper end is threaded as indicatedto receive therein a valve structure|22 generally cylindrical in external shape and threaded at its upperexternal end for assembly tothe portionA |Ba, being externally suitablyconformed as at |23 in the form of a nut so that it may be tightened upWith-suitable packingmaterial (not shown)l to make a tight joint.

The lower end of the valve structure |22 is of a diameterY to be looselyreceived Within the upperend of the spring-65and is bored out to providea downwardly facing annular ledge orA seat |24 againstwhichrests avalveelement |25 which is in thefform of a disk centrally apertured andcapable of movement downwardly awayfrom the seat |24 against theactionof a spring |2Eiwhich i-s housed within the lowerend ofthe valve str-udture and has itsl lower en'd abutting against a suitable plug |21provided with an aperture |28 preferably of substantial sizeincomparison to the aperture in the-valve element |25;

Along the axis of thevalve structure |22, its upper en'd is drilled andthreaded` to receivethe upper threaded portion of: a needle valvestructure |305. the lower endof the shank being-tapered off or giventhe' shapeof a cone; to formth'e-n'eedle element |3i' of the needlevalveV structure, for coacticn with the aperturein the disk-like'valveelement |25. The upper end of the threaded shank may be provided with ahead |32 knurled o'r otherwise-shapedso that' it may be convenientlyturned to'bring about theidesired relationship be'- tweenthe valveelements 25 andv |3'| and thereby, by' determining the extent to whichthe conical part |`3| projects into thev aperture in the valve element|25, to set the are'aof the valve opening when the'element |25 is in itsnormal uppermost position. Lock nuts I'Zila lockl the setting ofelements |3|.

The cored out chamber just above the valve ele'- ment I 25'is connectedby a pipe |33, suitably fixed, as by'v threading, into a hole in thelwall of the valve structure |22, and it extends through a' hole in thewallof the housing element l I8, with which it' is in sealed connectionas by brazing or the like.

The pipe |33 extends transversely of' the axis of the telescopic housing||'||`|8 and through suitable holes in the contiguous walls of thecylindrical. chambers 6'!v and 68 where it is connected to the housingelement ||8 of the tele- ||`|||8 and valve. structure related to thespring 66 and to the chamber 68,

12 being preferably of identical construction to that' above described,thus facilitating manufacture.

Since the parts that are related to the cylindrical chamber 58 areidentical to those related to the chamber 'i, they need not be describedin View of the foregoing and in Figure fr identical parts of the two areidentified by the same reference characters.

These two telescoping housing structures and valve structures may thusbe assembled as a sub-unit, made unitary vby the pipe connection |33 andas a unit laid into one half-section such as section 52 of the casingstructure 35, the Walls of the two half-'sections containing suitablehalves of the holes for receiving the portions ||8a and the pipeconnection |33, thus to facilitate laying the companion section 5i overthe section 52, thus completing these round holes, whence the sectionsare secured together and the nuts |2|l-` tightened up.

The lower side portion of valve structure |121. is milled or cut away,leaving side openings |34 that terminate above the threaded partcarrying the plug |21 and terminate below the underface ci valve member|25, so that downward movement of the latter by a distance greater thanthe thickness of member |25 makes openings i3d available for ow.

The interiors of the two telescoping housings, connected by the pipe|33, are filled with a suitable liquid such as oil, glycerine or thelike, and through the pipe connection |33 transfer of liquid from onespring housing to the other may take place but at respective rates thatmay be predetermined or set by the respective valve structures.

For example, when the arm 45 is forced in counter-clockwise direction,thus to cc'mpress spring 65 and to permit spring 66 to expand, theaccompanying upward movement oi housing part reduces the Volume in thehousing Iii-H51, puts the liquid therein under pressure, and liquid istransferred from the right-hand housing to the housing at the left inFigure 4, the vel e of the interior of which increases at the same rete,due to the mechanical connection by way of rock lever fil- 62 and thetwo moveable housing parts The rate at which transfer of liquid in thisdirection takes place and hence the rate at wl :h the counter-clockwisemovement of the arm Gt may take place is set by adjusting the size ofthe orifice or valve opening between the valve'elements |25 and |3|above the spring 55.

Liquid from the right-hand chamber thus flows through the plug aperture|28, through the valve orifice in valve element |25 and pipe |33, andthe resultant pressure, operating against the upper face of valve disk|25 in the left-hand structure, presses the latter downwardly againstthe spring |26, thus increasing the valve orifice and in effect removingresistance to flow of liquid into the expanding interior of theleft-hand structure i3, also by way of' openings |34 and aperture |28,equilibrium being established at a state of' compression of the spring65 and a state of expansion of the spring G5 according to thecircumstances that initiated the counter-clockwise swinging ofthe arm48.

Should the arm 4i) have been thus swung as a result of a landingoperation, the rebound effect may now be determined or set accordinglto, the setting of the valve elements in the lefthandhousingstr'uctureand the rate of clockwise swing of arm 40 thus suitedto the particular circumstances, by having initially adjusted therelationship between the valve elements |25 and I 3| above the spring35. When such reverse action takes place, the left-hand telescopichousing contracts and the right-hand one expands and the transfer ofliquid is now in reverse direction and hence from the left toward theright. The pressure of the liquid in the left-hand chamber lseats thevalve element |25 against its abutment |24, thus restoring the valveorifice to that for which elements |3| and |25 were initially set forthe lefthand structure, and now the rate of transfer of liquid from theleft-hand telescopic housing to the right-hand one is determined by thatoriiice or valve opening. In the right-hand housing, the pressure of theliquid against the upper face of valve element |25 presses the latterdownwardly against the spring |23, increasing the valve opening tofacilitate entry of liquid into the righthand expanding housing, andalso by way of openings |34 and aperture |28.

Thus, though the valve orices may be set for diierent rates of ejectionfor the two hydraulic housings, the setting of either of them forejection need not be affected by the action of the other on admission,for on admission, the normal or initially set valve opening becomesquickly enlarged under the pressure of the liquid 'seeking admission,for the downward movement of the valve element |25 relative to theconical valve element I3! can increase the size of the annular valveopening to suit the rate of admission flow, achieving a maximum when thepoint of the needle element 13| is substantially in the plane of theupper face of the element |25.

Accordingly, the action of each spring may be varied or supplemented byappropriate setting of the relationship of the valve elements |25 and|3| respectively associated with the two springs. For example, maximumvalve opening, by setting elements |3I, may be such that the two springsfunction solely like the two springs of Figure 3, while departures frommaximum valve opening can be made to determine the respective rates ofaction of the springs or can be made materially to supplement the actionof the springs and thus give the lstructure a greater load range than ifonly the springs were present as in Figure 3. Thus a wide variety ofoperating conditions met with in practice may be reliably met insubstantially one and the same unit of construction.

Where retractibility is desired, as earlier above mentioned, thecasing/,structure 35 and the parts rigidly connected thereto (Figures 1and 2) may be shifted or swung about the axis of the stud shafts 31-38within the range permitted by the angular spacing between the cut-outs3| and 32, illustratively about 90 as shown in Figure 1, where the partsare shown in extended position for landing or for handling of the craftwhen not in the air. In this position, the parts are held and locked bythe bottoming of stop element 41 in the cut-out 3| (Figure 1).

Stop element 41 is formed at the upper end of a slidable arm |35 havingat its lower end a yoke |31 between the upright or parallel arms ofwhich there is a sleeve or axially elongated collar |38 integrallyformed with or having secured to it a lever arm |43 provided at itsouter end with a suitable means such as an eye |4| for connection withany suitable operating mechanism such as a rod or link |42 by which thelever arm |.40and hence the sleeve |38 may be positively swung' ineither clockwise or counter-clockwise direction about its bearing uponstud shaft 31,

that being the axis about which the casing structure and related partsmay be pivoted or swung as earlier above described. The link |42 maylead to a manual control or to a mechanical relay or the like, of anysuitable construction, not shown, and as will be understood.

The yoke |31 has two spaced parallel internal faces |312 and |311 spacedapart by the diameter of the sleeve |33 so that the latter, though itswings about its axis, forms a guide for the lower end of the arm |33 inits up and down movement as viewed in Figure 1. At its upper end the arm|33 is also preferably guided and here the lateral walls of the stopelement 41, for purposes of such guiding, may engage the side walls of asuitable aperture formed in the underside of the righthand box structureas seen in Figure 2, the internal face of the detachable plate-like part45a forming one side of this guiding aperture and the two-partconstruction i5- 45a of the box facilitating assembly or disassembly.

The sleeve 33, rotatably supported on the stud shaft 31, is held againstsliding axially of the latter by any suitable means such as the bearingblock at the right-hand end of the sleeve |38 in Figure 2 and a collar|39 xed in any suitable manner to the shaft 31 at the left-hand end ofthe sleeve |33.

Suitable means are provided to urge the arm |33 (Figure l) toward theaxis about which the structure pivots, and for this purpose a spring |45may be employed. Thus, spring |45 may have its upper end entered in aradial cylindrical recess 31C formed in shaft 31; its lower portionextends into a hollow tube-like stud |46, shouldered at its lower end asat |433, spring |45 thus tending to project or force stud |46downwardly. Sleeve has an arcuate slot |33EL through which stud |43passes, its lower end entering a hole |318 in the lower transverse part|31h of the yoke |31 to the extent permitted by shoulder MGB. Stud |43thus holds arm |35 against displacement axially of the sleeve |33, andwith spring |45 pressing downwardly as viewed in Figures 1 and 2, thespring pressure is transmitted to the yoke |31 and hence to arm |36.

The sleeve or collar |33 has integrally formed therewith an upstandingcam element |49 shaped substantially as shown in Figure 1 and in linewith the longitudinal axis of the arm |36, the yoke has a recess |31dshaped to accommodate the cam |49 therein and of a depth such that, whenthe cam. i4@ is swung into alignment with the arm |35, the arm |35 maymove downwardly to an extent to withdraw the stop element 41 fromwhichever cut-out 3| or 32 it happened to be seated the spring |45insuring such Withdrawing movement.

To either side of the bottom of the recess |31d, the yoke faces arecurved as at |31e and |311, forming in eiect cam faces for coaction withthe cani element i From the above-mentioned intermediate or alignedposition of the cam |49, rotary movement of the latter in eitherdirection, under the control oi lever arm |40, effects rotary movementof the structure about the aXis oi the stud sha-its 317-33 and alsoultimate posive locking thereof in ultimate position.

In the positions shown in Figure 1, lever arm |47@ is in 'its maximumclockwise position and cam |49 is underneath the almost horizontalportion or the yoke-c surface |31f, with spring |45 compressed and withthe stop element 41 thus positively locked in the cut-out Y3| in theframe element I3.

'lloretract the structure, the controls are Aactuated to move the leverarm `|40 in counter-clockwise direction. A rst portion of such movementswings larm |40 about shaft 31, as permitted by the slot |383, thussliding cam |49 along the cam surface |31f, spring |45 bringing stop arm|36 downwardly and stop-element 41 being completely withdrawn from thecut-out 3| by the time that vcam |49 and recess |31d are in alignment.The next portion of the movement, being a continued counter-clockwiseswinging of lever arm |40, swings arm |36 and through the latter effectspivoting of the entire structure about the axis of -sha-fts 31--38, theengaging left-hand walls of cam |49 and of cam face |31d or the seatingof the cam |40 in the recess |31d insuring that arm |36 vswings with thecam, it being noted that reverse or upward movement of arm |36 isprecluded by the under-arcuate face of the frame element I3 once thestop element 41 is withdrawn from the cut-out 3| and a small initialswinging of the structure has taken place. Though stop 41 is vsowithdrawn, it remains seated in the guiding hole in block i5-45al andthus carries the entire structure around with it.

Appropriate, even if substantial, force applied to the lever arm U50 maythus insure the continued swinging of the structure in counterclochwisedirection as viewed in Figure 1, the boxes `45-45 (Figure 2) neatlyguiding the outer end of the moveable unit, and as soon as the stopelement 41 is brought into alignment with the cut-out 32, the cam |40and cam face i'ld may non7 partake of relative movement with the resultthat arm i325 is positively moved in the direction of its length andaway from the axis of pivoting, thus to enter the stop or lock element41 into the cut-out 32, halting pivoting movement of the unit but due toslot |3322 arm E35 swings further, throughout a third portion of themovement, to complete the swing o cam |49 in counter-clockwise directionto send lock element 41 completely into recess 32 and bring theoutermost end oi cam |49 underneath the almost horizontal portion of thecam face |31e, thus positively locking the structure in its new positionso long as the control lever arm |40 is held by any suitable means suchas its manual or other actuated mechanism, against retrograde movement.In this position of the parts the arm 40 with the landing devicescarried by it is in retracted position. The cables 9 |-92 or the cablesconnected to the eyes 51-59, for dirigibility, iiex appropriately as theabove movement in retraotiig dfi- *ection takes place, again becomingtaut when reverse movement and hence extension are completed.

Extension takes place, as will now be clear, by a reverse sequence ofsteps. Thus from its extreme left-hand position, for extension of thedevice, lever arm |40 is now positively moved in clockwise direction,the first portion of that movement being, due to slot |338, relative toshaft 31 and riding the cam |49 out from in under the lower portion ofthe cam surface |31e and into alignment with the recess |31d, whence thestop member 41 is withdrawn from the cut-out 32 under the action ofspring |45, and thereafter, with the right-hand face of cam |43 bearingagainst the right-hand face of recess |3101, the entire pivotal unitpivots with arm |36 about the axis of stud shafts 31--38 in clockwisedirection and when stop element 31 comes into alignment with an catchesin cut-out 3|, plvotting of the unit halts, but arm |40 continues toswing andcam |43 cams the yokeand arm |36 upwardly as viewed in Figure 1to project stop 41 completely into the cut-out 3|, bringing the cam |43underneath the almost horizontal portion of the cam face |31f andthereby also locking member 41 against movement out of the cut-out 3|.

1f desired, suitable stop elements may be provided on the auxiliaryframe in order denitely to x the limits of swing of the pivotal unit,and in Figure l I have shown two such stop elements in the form ofblocks EEZ-|53 screwed or otherwise secured to a side face of the frameelement i3 to be engaged by the box 45 in which the stop arm |36 isguided; they arc positioned at such respective points that the stopelement 41 is positively lined up with either of the cut-outs 3| oraccording to the direction of pivoting and which of the two steps|52-|53 is made effective.

also, it might be noted that the coaction between the spring |45, cam|49, and the two angularities formed at the upper ends of the guidefaces |31a and |31b of the yoke |31 may also be such as in eiect to lockthe lever |40 in either of its extremes of swinging movement. Thus, atthe extreme clockwise position shown in Figure 1, the cam |40 is to theright of its pivoting axis and extends into the angularity at the upperend of face |31b in which it is substantially Aheld by the downwardpressure of the now compressed spring |45. A similar action in theangularity at the upper end of the face i3d'a locks the lever in itsother extreme position. And, by making these angularities more acute orsomewhat less than a more positive locking action at each extreme may beachieved.

Where retractibility is not desired, the subunit may be easily andquickly mounted in position for caster-wheel action or for dirigibility,as illustratively indicated in Figures 6 and '7 where, for purposes ofillustration, it is assumed that the craft frame |55 terminates at itstail end in two frame elements IE6-|51 forming a V with an upright frameelement |58 at the apex.

1n such case, the lower bearing housing 15 (see also Figure 2) hassecured to it two arms |59 and |60 terminating in suitable split sleeveclamping elements |6| and |62 respectively by which, or any othersuitable means, the bracket arms IBS-|50 may be secured to the frameelements I56|51 respectively, while the upper bearing housing 8| (seealso Figure 2) may have secured to it suitable arms such as an arm |63extending rearwardly to the upright post |58 to which it may be securedin any suitable way as by the split clamping sleeve structure |64, andtwo laterally and downwardly extending bracket arms ISG and |61 securedrespectively to the frame elements |53 and |51, as by split clampingsleeve elements |68 and |10.

Thus it will be seen that the construction has wide range ofadaptability and if in the illustrai-ive arrangement of Figures 6-'1dirigibility is desired, the sheaves 33-89 may be utilized or the eyeleteiements 56-58, as was described above in connection with Figures 1 and2.

Thus it will be seen that there has been provided in this invention aconstruction in which the various objects above set forth together withmany thoroughly practical advantages are successfully schieved. Itwillbe seen that the construction is compact, is in its various partssimple to manufacture, its various subassemblies are easily andV quicklyeiected, and one sub-unit may easily and quickly be assembled to or withanother, and that wide range of adaptability is achievable. Moreover, itwillbe seen that the construction is well adapted to withstand thepeculiar and varying strains and stresses and is also capable ofhandling r being accommodated to a substantial range of different loador impact conditions met with in practice.

Also, it will be seen that the construction lends itself readily tonicely balanced action or control. For example, though, in the foregoingdescription, the lock member' ilY and its related control and operatingmechanism has been described as related to the element 13, the stopelement 4l and its control and operating mechanism maybe easilyduplicated and related to cut-outs 31-32 in the curved element i4, withthe operating lever and cam sleeve |38 pivoting about the stud shaft 38,all as shown in Figure 2'. In such case, the two lever arms |40 areoperated in synchronism by any suitable means (not shown) or, forexample, the two links |42 that lead to the two lever arms may bemechanically xed in any suitable way (not shown) to move in unison.

As many possible embodiments may be made ofv the above invention and asmany changes might be made in the embodiment above set forth, it is tobe understood that all matter hereinbefore set forth or shown in theaccompanying drawings is to be interpreted as illustrative and not in alimiting sense.

I claim:

1. In construction of the character described, in combination, an arm.for supporting a landing device at one end and having at the other end apivotal support with lever arm means extending therefrom, two companioncasing parts, said other end extending intol and between said twocompanion casing parts, spring means, said casing parts having thereincompanion chamberforming walls for housing, when assembled together,said spring means for coaction with said lever arm means, said twocasing parts having means coacting with the pivotal support of said armfor pivotally supporting it and having companion extension meansforming, when said casing parts are secured together, an axis aboutwhich said casing may p-ivot, bearing means coacting with said companionaxis-forming means for pivotally supporting said casing, means forsupporting said bearing means to swing about an axis extending at anangle thereto, and means for controlling the direction and extent ofswinging thereof. n

2. In construction of the character described, in combination, an armfor supporting a landing device at one end and having at the other end apivotal support with. lever arm means extending therefrom, two companioncasing parts, said other end extending into and between said twocompanion casing parts, spring means, said casing parts having thereinvcompanion chamberforming walls for housing, when assembled together,said spring means for coaction with said lever arm means, said twocasing parts having means coacting with the pivotal support of said armfor pivotally supporting it and having companion extension meansforming, when said casing parts are secured together, an axis aboutwhich said casing may pivot, spaced bearing means for pivotallysupporting said casing and coacting with said axis-forming means, meanspivotally supporting one of said spaced bearing means, and meanscomprising an arcuate guiding element coacting with the other of saidspaced bearing means during pivoting of said casing y158 structure aboutthe pivotal support of said one of said spaced bearing means. n

3. A construction as claimed in claim 2 provided with locking means,said locking means comprising spaced locking recesses in said arcuateguiding meansan-d a lock member having means mounting it for movementalong a radius with the axis of said one spaced bearing means atsubstantially its center, nand a lever arm iorswing'- ing said casingabout the axisl o'f-said one spaced bearingv means and for controllingthe position eff said lock member.

e.. A construction as claimed in claim- 2 provided with locking means,said locking means comprising spaced locking. recesses in said arcuateguiding means 'and' a lock member having means mounting. it for movementalong a radiuswith the axis of said one spaced bearing means atsubstantially its center, means adapted upon movement to swing saidcasing about said pivoting. axis of said one of said spaced bearingmeans and `having a lost motion connection. therewith, and meansresponsive to the action of said. lost motion. connection forcontrolling said lockmer'riber.

5. In construction of the character described, in combination, aframe,an arm for supportingK a landing device at oneA end and having at theother end a pivotal support with lever arm means extending therefrom,-two companion casing parts, said other end extending into and betweensaid two companion casing parts, spring means, said casing parts havingtherein companion cham-berorming walls for housing, when assembledtogether, said spring. means for coacting with said lever `arm means,said two casing parts having means coacting with the pivot of saidarmior pivotally supporting. itandv means for holding said casing partsassembledandmeans connected with said secured-together casing parts forpivotally supporting them` a-nd said arm from said frame as a unit toswing about a horizontal axis for thereby retracting or extending saiddevice, said last-mentioned means including means' providing a verticalYaxisv of pivoting forsaid securedtogether parts whereby said parts' andarm and device may movek also about said vertical axis.r

6. In construction of the character described, in combination, an armfor supporting a landing device at one end and having at the other end apivotal support' withv lever arm means extending therefrom, twocompanionc'asing parts, said other end extending into andv between saidtwo com'- panion casing; parts; springl means, said casing'v partshaving therein companion chamber-forming walls for housing, whenassembled together, said spring means for coacting with said lever armmeans, said two' casing parts having means eoacting with the pivot ofsaid arm for pivotally supporting it, means forming a variable chamberencased by said casing parts and receivable therebetween upon assemblyand having means responsive to pivoting movement of said arm to f varythe volume thereof, and means forming a fluid connection to saidvariable chamber and including means for controlling fluid flow to andfrom said variable chamber to thereby vary the rate of change ofv volumeof` said variable chaming. device at one end. and having at the othervend a pivotal support with lever arm means ex-` tending therefrom, twocompanion casing parts said other end extending into and between saidtwo companion casing parts, spring means, said casing parts havingtherein companion chamberforming walls for housing, when assembledtogether, said spring means for coaction with said lever arm means, saidtwo casing .parts having means coacting with the pivot of said arm forpivotally supporting it, means forming a variable chamber encased bysaid casing parts and receivable therebetween upon assembly and havingmeans responsive to pivoting movement of said arm to vary the volumethereof, said variable chamber containing a fluid, and means includingcontrollable valve means in connection with said chamber for controllingthe rate of ejection or admission of iluid as the volume of said chamberis varied by said arm.

8. In construction of the character described, in combination, a supporthaving means moveyably supporting a member carrying a landing devicewhereby said landing device may move toward and then away from saidsupport, a differentiallyacting hydraulic means acting upon said memberto oppose movement of said member toward said support and capable ofyielding at a certain rate under adequate load or impact, and meanschanging the differential between said two hydraulic means forcontrolling the rate at which said member thereafter moves away fromsaid support upon lessening or removal of the load.

9. A retractible and extendible landing gear comprising a main supporthaving means for supporting a landing device, means providing a pivotalsupport for said main support to swing about a substantially horizontalaxis for thereby retracting or extending said device, means for lockingsaid main support at either of two positions to swing about said axiscorresponding substantially to retraction or extension of said device,and reversible mechanism for effecting swinging of said main support andfor controlling said locking means, said mechanism operating in a cycleof steps of which the rst effects unlocking of said locking means, thesecond eiects swinging of said support about its axis, and the thirdeffects locking of said locking means.

10. A retractible and extendible landing gear comprising a main supporthaving means for supporting a landing device, means providing a pivotalsupport for said main support to swing about a substantially horizontalaxis for thereby retracting or extending said device, locking meanscomprising a lock member having means mounting it for swinging movementwith said support and companion locking means having means mounting itfixedly in position to coact with said locking member in either of theextremes of pivoting movement of said support, a lever having meansmounting it to pivot about said axis and having means forming alost-motion connection with said support, and means responsive to thelost motion in said connection for actuating said locking member.

11. A retractible and extendible landing gear comprising a main supporthaving means for supporting a landing device, means providing a pivotalsupport for said main support to swing about a substantially horizontalaxis for thereby retracting or extending said device, locking meanscomprising a lock member having means mounting it for swinging movementwith said support and companion locking means having means mounting itflxedly in position to coact with said locking member in either of theextremes of pivoting movement of said support, a lever having meanspivotally mounting it, and coacting cam means associated respectivelywith said lever and with said locking member and constructed to controlmovement of said locking member in un-locking direction in response to afirst stage of movement of said lever, then to swing said support aboutits pivot in response to a succeeding stage of movement of the lever,and in a nal stage of movement of the lever to control movement of saidlocking member in locking direction.

12. In construction of the character described, in combination, asupport having means moveably supporting a member carrying a landingdevice whereby said landing device may move to- Ward and then away fromsaid support, two means forming chambers capable of having their volumev-aried and having means mechanically connecting and relating them tosaid member so that the volume of one increases as the volume of theother decreases in response to transmission thereto by said connectingmeans of movement of said member relative to said support, means forminga connection between said two chambers for interchange of fluidtherebetween, and combined discharge and admission valve means for eachchamber for controlling the rate of iluid interchange, and means forrendering one of said valve means ineffective for controlling said rate0f interchange responsive to fluid interchange in one direction andmeans rendering the other of said valve means ineffective forcontrolling said rate of interchange responsive to fluid interchange inthe opposite direction.

13. In construction of the character described, in combination, asupport having means moveably supporting a member carrying a landingdevice whereby said landing device may move toward and then away fromsaid support, two means forming chambers capable of having their volumevaried and having means mechanically connecting and relating them tos-aid member so that the volume of one increases as the volume of theother decreases in response to transmission thereto by said connectingmeans of movement of said member relative to said support, means forminga connection between said two chambers for reversible iiow of iiuidbetween said two chambers and including controllable discharge valvemeans, one for each chamber, and admission valve means, one for eachchamber, the admission valve means of one chamber having a flow factorat least as great as the ow factor of the discharge valve means of theother chamber.

14. In construction of the character described, in combination, asupport having means moveably supporting a member carrying a landingdevice whereby the latter may move toward or away from said support, twospring means having means relating them to said member so that oneyieldingly opposes movement of said member toward said support and theother yieldingly opposes movement of said member away from said support,means enclosing said two spring means and forming a chamber for eachthat is expandible or contractible and hence of variable volume, meansforming a uid connection between said two chambers, and means forcontrolling the rate of interchange of fluid therebetween.

15. In construction of the character described, in combination, asupport having means move ably supporting a member carrying a landingdevice whereby the latter may move toward or away from said support, twospring means having means relating them to said member so that oneyieldingly opposes movement of said member toward said support and theother yieldingly opposes movement of said member away from said support,two hydraulic piston and cylinder means having a iiuid connectiontherebetween and means mechanically relating each of them to said memberso that the volume of one increases and the volume of the otherdecreases in response 'to transmission thereto by saidmechanically-relating means of movement of said member relative to saidsupport, and valve means capable of xing diierent rates of flow for thetwo directions of interchange of i-uid between said two piston andcylinder means.

16. In construction ci the character described, in combination, asupport having means mov- Vably supporting a member carrying a landingdevice whereby said landing device may move toward and then away fromsaid support, two means forming chambers capable of having their volumevaried and having means mechanically connecting and relating them tosaid member so that the volume of one increases as the volume of theother decreases in response to transmission thereto by said connectingmeans of movement of said member relative to said support, means forminga connection between said two chambers for reversible ow of fluidbetween said two chambers and including a combined discharge andadmission valve means, one for each chamber and each comprising an oricemember, means for varying at will the eiective size of each orice fordischarge flow, and yielding means responsive to pressure of iiuid owingin admission direction for decreasing the restriction of the rate ofintake of fluid according to the pressure thereof.

17. In construction of the character described, in combination, asupport having means movably supporting a member carrying a landingdevice whereby said landing device may move toward and then away fromsaid support, two means forming chambers capable of having their volumevaried and having means mechanically connecting and relating them tosaid member so that the volume of one increases as the volume of theother decreases in response to transmission thereto by said connectingmeans of movement of said member relative to said support, means forminga connection between said two chambers for reversible ow of iiuidbetween said two chambers and including a combined discharge andadmission valve means, one for each chamber and each comprising anorifice member, valve means for varying at will the effective size ofeach orifice for discharge ilow, means mounting said orifice member formovement away from said valve means in response to pressure -of fluidflowing in admission direction to decrease the restriction of the rateof intake of iiuid, and port means coacting with such aforesaid movementof the orifice member for admission of fluid into the chamber.

18. In construction of the character described, in combination, an armfor supporting a landing device at one end and having at the other end apivotal support with lever arm means extending therefrom, two companioncasing parts, said other end extending into and between said twocompanion casing parts, spring means, said casing parts having thereincompanion chamberforming walls for housing, when assembled together,said spring means for coaction with said lever arm means, said twocasing parts having means coacting with the pivot of said arm forpivotally supporting it and moveable (pistonlike) piston and cylindermeans receivable within and encased by said two casing parts whenassembled for coaction with said spring means upon said lever arm meansof said arm, a fluid within said cylinder means and fluid valve meanscommunicating with said cylinder means for controlling fluid flow intoand out of said cylinder means.

19. In construction of vthe character described, in combination, an armfor supporting a landing device at one end and having at the other end avpivotal support with lever arm means extending therefrom, two companioncasing parts, said other end extending into and between said twocompanion casing parts, spring means, said casing lparts having thereincompanion chamberforming walls for housing, when assembled together,said spring means for coaction with said lever arm means, said twocasing parts having means coacting with the pivot of said arm forypivotally supporting it and piston and cylinder means responsive toiiuid under pressure and encased by said casing and receivable betweenthe two parts thereof upon assembly and constructed for coacting withsaid lever arm means to modify the action of said spring means upon saidlever arm means, means securing said companion casing parts together,and a iluid for coacting with said fluid-responsive means.

20. In an aircraft landing gear, in combination, a support, a casingthereon having therein Itwo spring means, a member for supporting alanding device and having a part extending into said casing, with meansmovably supporting it relatively to said casing whereby said landingdevice may move toward and away from said support, one of said springsbeing normally under stress and acting u-pon said part in a. directionaiding movement of said landing device toward said support and the otherof said springs acting upon said part in the direction opposing movementof said landing device toward said support and being of a stiinessgreater than said rst spring to thereby resist the stress imposedthereon by said normally-stressed spring.

ALDO M. FRANCHI.

REFERENCES CITED The following references are of record in the rile ofthis patent:

UNITED STATES PATENTS Number Name Date 963,650 Raymond July 5, 19101,111,924 Smith Sept. 29, 1914 1,752,183 Kell Mar. 25, 1930 1,847,491Messier Mar. 1, 1932 1,928,816 Grayson Oct. 3, 1933 2,011,460 SnyderAug. 13, 1935 2,021,306 Hathorn Nov. 19, 1935 2,077,934 Johnson Apr. 20,1937 2,206,800 Armstrong July 2, 1940 2,240,892 Meyer May 6, 1941FOREIGN PATENTS Number Country Date 359,466 Great Britain Apr. 15, 1930520,944 Great Britain May 8, 1940 819,026 France June 28, 1937

